Is possible it is a bit of smell is normal? I guess not since it was coming into the house. There is a pipe coming out the side, so i put a stick down it i was hard could not get through. I guess i have to dig up the top and check....

I talked to a pump out guy, he says the water should not be a problem and i should just fill it in and leave the hatch off. Since it's his business i guess we can rely on that answer since he could have made money off me.

I'm think now the smell was coming from a leak from the sewer connection when they hooked it up. Probably in the soil that is in pile now.

The Abs elbow 90 degrees then a female connector to the 4' sewer pipe with the rubber gasket. The female being smaller perhaps slipped off by the soil sinking, maybe a car or truck drove over the lawn.

Haven't notice the smell for a while. I think it's gone.

The open septic has no smell so i guess no problem. How could there be after 10 or 20 years?

I suppose there will be lots of soil left over from this excavation so just as well to put in the old tank now.

1st, don't leave it open for any time, friends of mine had one open waiting for a pump truck and lost a 2 year old baby in it.
We always had to get them pumped break down the lid all of it and over fill it with sand wet it down so the sand would settle Compact before covering, the fear was a home for rats and things.

When a soil becomes water logged, it provides the perfect conditions for anaerobic bacteria, which are a type of microorganism that can only survive in the absence of oxygen. Soil with anaerobic bacteria will have a very bad smell. Soils in low, poorly-drained areas with lots of clay or organic matter are the most likely to provide the necessary conditions for this type of noxious bacterial. The same conditions can develop in houseplants if the pots are not well drained or if they are over-watered.